I thought I saw the other day a news highlight that that this (link below) is going to become an effort at the federal level by this summer...people will be able to opt-in to this "registry" at no charge:

http://www.puc.state.tx.us/ocp/telephone/donotcall .cfm

does not the solve the e-mail spam or potential sms abuse, but looks to address the PSTN portion (in the US), I think, relative to ENUM implementation?